Pursuant to the networking of in-vehicle equipment and the increase of in-vehicle software, the necessity of introducing information security technologies is also being recognized in the automobile sector. In particular, the service of distributing and updating the firmware of ECUs (Electric Control Units) from an external information processing device via wireless transmission is now being put into practical application, and the necessity of introducing security technologies for the foregoing firmware update is increasing.
PTL 1 discloses an invention in which, in a communication system configured from an ECU, a center, and a rewriting device existing on a communication path connecting the ECU and the center, when the center authenticates the rewriting device, the center sends, to the rewriting device, secret information required for rewriting the firmware of the ECU.